An excellent high-temperature oxide superconducting wire is conventionally manufactured by epitaxially growing a layer of an oxide such as cerium oxide (CeO2), yttria-stabilized zirconia (YSZ), or yttrium oxide (Y2O3), as an intermediate layer, on a metal substrate by a sputtering method or the like, and then epitaxially growing a superconducting compound layer (RE123 film, RE: Y, Gd, Ho, or the like) thereon by a laser ablation method or the like.
Methods known as techniques for obtaining a crystal-oriented superconducting compound layer are: an ion-beam-assisted deposition method (IBAD method) that involves depositing a textured intermediate layer on a non-textured metal substrate such as hastelloy, so as to transfer the crystal orientation to a superconducting compound layer; and a method (e.g., RABiTS (Rolling-Assisted Biaxially Textured Substrate) method) that involves performing deposition while transferring the crystal orientation to an intermediate layer and to a superconducting compound layer with the use of a biaxially crystal-oriented metal substrate. The latter method is more advantageous than the former in view of future production efficiency factors such as film deposition rate. High biaxial crystal orientation of a metal substrate is required for improvement of superconductivity.
A substrate known as such a metal substrate (substrate for a superconducting wire) is produced by laminating crystal-oriented copper on a stainless substrate, and then further laminating nickel thereon. For example, Patent Document 1 discloses a clad textured metal substrate for forming an epitaxial thin film comprising a metal layer and a copper layer bonded to at least one surface of the metal layer. The copper layer has a {100} <001> cube texture wherein the drift angle of the crystal axis is Δϕ≤6°.
Furthermore, as a method for manufacturing a biaxially crystal-oriented metal substrate, Patent Document 2 discloses a method for manufacturing a metal laminated substrate for an oxide superconducting wire, which comprises laminating a nonmagnetic metal plate made of stainless steel or the like and a metallic foil made of Cu or a Cu alloy, which has been cold-rolled at a high reduction, through surface activation bonding, biaxially crystal-orienting the metallic foil by heat treatment after lamination, and thus providing an Ni or Ni alloy epitaxial growth film on the surface of the metallic foil.